Can Probiotics Prevent Asthma?

Prenatal probiotics have been shown to help prevent atopic dermatitis, but are they effective in preventing asthma? Unfortunately, it seems not, say researchers from the University of Alberta, the University of Manitoba, and the Manitoba Institute of Child Health, all in Canada. The researchers analyzed data from randomized controlled trials of pregnant women or healthy infants but found no evidence to support a protective association between perinatal probiotics and childhood asthma or wheeze.

In 9 trials involving 3,257 children, the incidence of doctor-diagnosed asthma at final assessment was 11.2% among patients who received probiotics and 10.2% among those receiving placebo. In 9 trials involving 1,949 children, incident wheeze was similar after supplementation with probiotics (35%) vs placebo (31%). Two other trials reported an increased risk of recurrent wheeze after probiotics, and a third reported a lower risk.

However, although “inadequately reported,” the researchers say, probiotics could be associated with clinically relevant increases in lower respiratory tract infections (RTIs). Six trials involving 1,364 children that had data on lower RTIs found an incidence of 14.5% among children who received probiotics, compared with 13.2% among those who received placebo. Notably, the researchers say, 4 of those trials documented lower RTIs nonsystematically as adverse events rather than as primary or secondary outcomes. When those 4 trials were excluded, the pooled risk ratio of lower RTI associated with probiotics was 1.11.

Subgroup analyses revealed that the effect of probiotics was similar regardless of timing (prenatal, postnatal, or both) or person receiving the intervention (mother, infant, or both). The researchers also note that the large variety of strains, combinations, and doses tested made it hard to assess efficacy of specific probiotic organisms.

Future research, the authors say, could help identify infants most likely to benefit from probiotics. They cite research that has shown probiotics were protective against IgE-associated allergic disease in infants delivered by cesarean section (whose gut microbiota is disrupted) but not in their vaginally delivered counterparts. They suggest that probiotics might play a useful role in other microbiota-disrupting exposures, such as formula feeding and antibiotic treatment. But so far, they conclude, evidence is insufficient to support recommending perinatal probiotics for primary prevention of asthma or wheeze.

Source
Azad MB, Coneys JG, Kozyrskyj AL, et al. BMJ. 2013;347:f6471.
doi: 10.1136/bmj.f6471.